1. Field of the invention.
The present invention relates to a laser shock peening apparatus, and more particularly, to a method and apparatus for utilizing a multiple beam dispenser in a plurality of laser peening cells.
2. Description of the related art.
Laser shock peening is a process for improving the fatigue, hardness, and corrosion resistance properties of materials by focusing radiation on preselected surface areas of a workpiece. Laser shock peening the workpiece can avoid gross deformation, cracking, and spallation of the workpiece, and nonplanar workpieces can be laser shock processed without the need of elaborate and costly shock focusing schemes.
Laser peening, or also referred to as laser shock processing and laser shock peening, typically utilizes two overlays: a transparent overlay (usually water) and an opaque overlay, typically an oil based, acrylic based, or water based, black paint. During processing, a laser beam is directed to pass through the water overlay and is absorbed by the black paint, causing a rapid plasma formation and vaporization of the paint surface and the generation of a high amplitude shock wave. The shock wave cold works the surface of the workpiece and creates compressive residual stresses, which provide an increase in fatigue properties of the part. When using a water-based paint, a high-speed water jet quickly removes any remaining paint on the workpiece, and the workpiece surface is subsequently dried by the use of a high-pressure fluid or gas jet.
Finally, the workpiece is repositioned for further processing. A workpiece is processed by producing a matrix of overlapping spots that cover the fatigue critical zone of the part.
The entire laser-peening process occurs inside a peening cell, wherein a part manipulator positions the workpiece. Laser systems used for laser peening are typically interfaced to a single laser peening cell. Consequently, there are limits to the types of workpieces that can be laser peened with single-peening-cell configurations. Additionally, the laser system cannot be utilized during initial workpiece set-up and alignment, which results in significant loss of productivity and higher laser peening costs.